Air Speed Research Articles

Effect of ventilation strategy on performance of upper-room ultraviolet germicidal irradiation (UVGI) system in a learning environment

Upper-room ultraviolet germicidal irradiation (UVGI) system is recently in the limelight as a potentially effective method to mitigate the risk of airborne virus infection in indoor environments. However, few studies quantitatively evaluated the relationship between ventilation effectiveness and virus disinfection performance of a UVGI system. The objective of this study is to investigate the effects of ventilation strategy on detailed airflow distributions and UVGI disinfection performance in an occupied classroom. Three-dimensional computational fluid dynamics (CFD) simulations were performed for representative cooling, heating, and ventilation scenarios. The results show that when the ventilation rate is 1.1 h−1 (the minimum ventilation rate based on ASHRAE 62.1), enhancing indoor air circulation with the mixing fan notably improves the UVGI disinfection performance, especially for cooling with displacement ventilation and all-air-heating conditions. However, increasing indoor air mixing yields negligible effect on the disinfection performance for forced-convection cooling condition. The results also reveal that regardless of indoor thermal condition, disinfection effectiveness of a UVGI system increases as ventilation effectiveness is close to unity. Moreover, when the room average air speed is >0.1 m/s, upper-room UVGI system could yield about 90% disinfection effect for the aerosol size of 1 μm–10 μm. The findings of this study imply that upper-room UVGI systems in indoor environments (i.e., classrooms, hospitals) should be designed considering ventilation strategy and occupancy conditions, especially for occupied buildings with insufficient air mixing throughout the space.

Quantification of the Relationship of Pyridoxine and Spirometry Measurements in the United States Population

BackgroundThere has been evidence to suggest associations between vitamins and lung function. ObjectiveThis study aimed to examine the association between vitamin B6 and spirometry values. MethodsA cross-sectional study was done using National Health and Nutritional Examination Surveys (NHANES) 2007–2012, which is a nationally representative, modern cohort. Spirometry, a clinical pulmonary function test, measured the amount and speed of air a person could exhale after taking the deepest possible breath after forceful expiratory volume at 1 s (FEV1) and forced vital capacity (FVC). After determination of the relationship of the linearity of variables, univariable and multivariable models were fitted to investigate the effect of vitamin B6 on FEV1 and FVC. The National Center for Health Statistics Ethics Review Board granted permission for the study’s data collection and analysis. ResultsOf 19,160 individuals who had complete information on vitamin B6 intake, FEV1, and FVC, it was found each mg of vitamin B6 intake was associated with increase in 166.41 mL of FEV1 (95% CI: 156.71, 176.12; P < 0.01) and 221.6 mL of FVC (95% CI: 209.62, 233.57; P < 0.01). After controlling for potential confounders (age, race, sex, body mass index, education, and income), multiple linear regression found that each mg of vitamin B6 was associated with increase in 25.98 mL of FEV1 (95% CI: 19.15, 32.80, P < 0.01) and 38.97 mL of FVC (95% CI: 30.65, 47.30, P < 0.01). ConclusionIncreased vitamin B6 intake is associated with improvement in lung function. Further prospective studies are required to ascertain whether increased vitamin B6 can lead to increased long-term spirometry measurements and the specific therapeutic dose–response relationship.

Automatic interval management for aircraft based on dynamic fuzzy speed control considering uncertainty

A novel real-time autonomous Interval Management System (IMS) is proposed to automate interval management, which considers the effect of wind uncertainty using the Dynamic Fuzzy Velocity Decision (DFVD) algorithm. The membership function can be generated dynamically based on the True Air Speed (TAS) limitation changes in real time and the interval criterion of the adjacent aircraft, and combined with human cognition to formulate fuzzy rules for speed adjusting decision-making. Three groups of experiments were conducted during the en-route descent stage to validate the proposed IMS and DFVD performances, and to analyze the impact factors of the algorithm. The verification experimental results show that compared with actual flight status data under controllers’ command, the IMS reduces the descent time by approaching 30% with favorable wind uncertainty suppression performance. Sensitivity analysis shows that the ability improvement of DFVD is mainly affected by the boundary value of the membership function. Additionally, the dynamic generation of the velocity membership function has greater advantages than the static method in terms of safety and stability. Through the analysis of influencing factors, we found that the interval criterion and aircraft category have no significant effect on the capability of IMS. In a higher initial altitude scenario, the initial interval should be appropriately increased to enhance safety and efficiency during the descent process. This prototype system could evolve into a real-time Flight-deck Interval Management (FIM) tool in the future.

Statistical and fuzzy modeling for accurate prediction of feed intake and surface temperature of laying hens subjected to light challenges

The use of artificial lighting for laying hens in poultry houses allows production optimization. However, the effect of recent lighting technologies needs to be investigated, as their use can affect the welfare of hens, causing biological rhythm, behavior, health, productive and reproductive performance and egg quality changes. Therefore, the objective of this study was to evaluate the physiological responses, productive performance and egg quality of hens under different light intensities. If a significant difference between treatments was found, statistical models and fuzzy inference systems (FISs) to predict such responses were developed and compared. Thus, 76 Hy-Line W-80 laying hens were housed in a controlled environment with temperature, relative humidity and air speed adjusted for bird comfort. The hens were exposed to illuminances of 5, 20, 50 and 100 lx for a period of 21 days. Among the evaluated response variables, only the mean feed intake (FI) and surface temperature (tsurf) of the hens had a significant interaction and interaction sliced by main factors (p < 0.05), allowing statistical model adjustment. For these two variables, FISs were also developed so that the illuminance and the time of exposure to illumination (tillu) were defined as input variables of the systems. As a result, the statistical models and FISs presented significant high-accuracy indexes when predicting the FI and the tsurf (except for R2 values related to the statistical models), yet with an advantage for the FISs models, in which greater generalization capabilities were obtained in the validation step. Therefore, the developed models can be used to support decisions related to the management of hens, supporting the smart production, with emphasis on FISs based on expert knowledge, since they can be used to obtain predicted responses in different scenarios in addition to those evaluated experimentally with high accuracy.

Experimental Study on the Influence of Working Parameters of Centrifugal Fan on Airflow Field in Cleaning Room

The air distribution and speed uniformity of the cleaning fan in the cleaning room have a great influence on the working quality of the cleaning system of the harvester. In view of the problem of uneven air distribution in the cleaning room caused by improper adjustment of the main operating parameters of the cleaning fan in the cleaning device of the corn combine harvester, this paper takes the self-developed air screen cleaning test bench as the object. The main working parameters of the cleaning centrifugal fan (air supply distance, fan speed, and number of blades) were simulated and the Fluent simulation software was used to carry out the single-factor and multi-factor optimization tests, explore the influence law of each test factor on the air velocity in front of the screen, in the middle and behind the screen and the deviation degree of the airflow at the back of the screen surface, and find the optimal parameter combination. The data were systematically analyzed by multiple regression method and variance analysis method. The regression model of air velocity at the front, middle, and back of the screen and the air deviation degree at the back of the screen surface for the three working parameters of the cleaning fan were established. The optimal working parameter combination was obtained, that is, when the air supply distance is 580 mm, the fan speed is 1000 r/min, and the number of blades is 10, the airflow velocity in front of the screen is 10.8 m/s, the airflow velocity in the middle of the screen surface is 11.8 m/s, the airflow velocity at the back of the screen surface is 11.2 m/s, and the airflow deviation degree at the back of the screen surface is 13.5%. The relative errors were 1.9%, 0, 2.8%, and 3.0%, respectively. A combined test of the fan and the cleaning screen body with a feeding capacity of 8 kg/s was carried out, and the loss rate was 1.15% and the impurities rate was 1.24%. The regression model was reliable, and the optimal operation parameter combination performed well, meeting the technical requirements of cleaning operation, and providing theoretical guidance for the adjustment of fan structure and operation parameters in the cleaning system of the grain harvester.

Air speed and plastic crate vent-holes for wine grape quality during postharvest dehydration: commercial and laboratory studies.

Airflow is an important issue to favor postharvest dehydration keeping wine grape quality. The aim of this experimental work was to analyze the grape quality during postharvest dehydration: (i) in a commercial facility ('fruttaia') by monitoring the efficiency of the ventilation system and (ii) at laboratory level, studying the influence of crate type and airflow direction. In the fruttaia, the airflow was provided by an air duct hanging from the ceiling, and by floor fans. A great gap in air speed from 0 up to 3.7 m s-1 was measured in different sectors of the fruttaia, leading to a different weight loss and grape quality in crates, depending on crate stack height and sector. At the laboratory level, two tunnels, with exhaust or supply fans, were used and four crate types with different percentages of vent-holes were adopted. A decrease of about 5% delayed the weight loss rate depending on the type of crate, and the exhaust fan guaranteed a faster dehydration. The results clarified the inefficiency of the commercial ventilation system in ensuring homogeneous grape weight loss in all crates. In addition, the exhaust fan guaranteed a more uniform air distribution around crates, and a slightly higher air speed. © 2023 Society of Chemical Industry.

Experimental Investigation for Augmentation of Thermal Performance of Solar Air Collector

This paper presents a study of the thermal performance of a solar air collector used to heat the drying air of a fruit and vegetable dryer. The prototype collector could be a viable solution to improve energy efficiency and food security in Burkina Faso and other developing countries, by contributing to the reduction of post-harvest losses and the increase of income for local agricultural producers. The collector is first realized by using black painted cans as air ducts, perforated to increase turbulence, and a glass covering the collection surface. After realization, the collector is connected to the dryer and a measurement campaign is conducted to evaluate the thermal performance of it. The measured parameters are the sunshine and the air temperature by keeping the air speed fixed at 0.3 m/s. The analysis of the results shows an important variation of the air temperature difference going from 0.1°C to 74.4°C, between the inlet and the outlet of the collector for an irradiation which varies between 142 W/m2 and 837 W/m2. The black painted surface of the air ducts as well as the increase in turbulence contributed to improve the efficiency of the collector which varies between 0.94% and 50.68% and allowing to record air temperatures ranging from 27.2°C to 69.2°C inside the dryer. This temperature range is favorable for the drying of most food products.

Analisis Penggunaan Winglet Pada Pesawat Udara Cessna 150 Dengan Profil NACA 2412

The Cessna 150 is a light aircraft that is widely used in the world of general aviation. One important aspect in designing an aircraft, including the Cessna 150, is the wing design. When there is a meeting of air flows with different pressures from the top and bottom of the aircraft wing, it can cause a vortex to form at each wing tip. The impact of this vortex is that drag force increases, lift force and fuel efficiency decrease and turbulence can occur. One modification to aircraft wings to reduce the impact of these vortices is the use of winglets. This has been widely applied to the latest commercial aircraft to increase aircraft efficiency. The aim of this research is to analyze the use of winglets on a Cessna 150 aircraft with a NACA 2412 profile. This research uses Xflr5 numerical simulation with a 3D geometric configuration. The winglet shape used is cant angle with bend angles of 0°, 15, 30°, 60°, and 90° which were tested at angles of attack of 0°, 3°, 6°, 9°, 12°, 15°, and 18° with an air speed of 46 m/s. The research results show that the NACA 2412 airfoil with winglets is able to increase wing performance efficiency. This is proven by the visualization of air flow in modifications with winglets which can reduce vortices so that the air flow becomes smoother/laminer. In addition, numerical studies show an increase in the value of the lift coefficient (CL), a decrease in the value of the drag coefficient (CD), , and a better / ratio (CL/CD) with the use of winglets, where the winglet efficiency is best at a cant angle with a bend angle of 30°.

Uniform exhaust characteristics of new-type airbox components of continuous miner

When the dust removal system of the continuous mining machine works, the exhaust air volume cannot meet the design requirements due to the different pressure and uneven air speed in the exhaust duct. These will lead to an increase in the energy consumption of the fan. In this paper, the uniform exhaust mathematical model was established. A novel resistance plate member was developed on the basis of a uniform exhaust pipe with variable cross sections. The uniform exhaust characteristics of two different exhaust ducts were discussed. The influence of adding a resistance plate on the vibration characteristics of airbox components was analyzed. The results show that adding resistance plate members could significantly reduce the airflow resistance, deviation, and unevenness of the exhaust rate. When the excitation frequency is 130 Hz, the vibration response of the airbox components is stronger, and operation at this frequency should be avoided.

Analysis of Dust Reduction Characteristics of Multistage Tandem Dust Removal System

Asphalt hot regeneration pavement maintenance vehicle is a type of in situ heating waste asphalt special vehicle equipment for mix and regeneration of aged asphalt. When waste asphalt mixture is heated and melted, a lot of organic fumes are typically produced, along with dust from the mixing process. Because of the complex composition of the exhaust gases produced by asphalt hot regeneration pavement maintenance vehicles, it can be difficult to purify and remove them using a single method. In order to effectively purify exhaust gas with complicated compositions, a multistage combined treatment dust removal system structure is presented that includes cyclone sections, spray sections, and adsorption sections. With an emphasis on the cyclone section structure with the dust-gas separation function, computational fluid dynamics (CFD) is used to analyze the internal flow field characteristics, turbulence intensity, tangential velocity, and velocity field vector characteristics. The results reveal that the more symmetrical the distribution of tangential velocity field and static pressure field is, the greater the cyclone dust collector’s dust removal efficiency is, the more stable the flow field is, and the lower the turbulence intensity is. Furthermore, the center cyclone’s growing speed is adversely connected with dust removal effectiveness. As a result, an antiventuri cyclone dust collector with a scrambling column was designed. When the inlet air speed is 6 m/s, the dust removal efficiency of the improved device is 97.0%, which is 5.1% higher than that of the original device, and when the inlet air speed is 8 m/s, the dust removal efficiency of the improved device is 97.3%, which is 4.16% higher than that of the original device. With the increase of the inlet air speed, the difference between them keeps decreasing.

CFD-Based Approach to Propose a Zigzag-Shaped Tube Heat Exchanger without Fins

This study explores the application of zigzag-shaped, finless tubes in enhancing heat transfer performance within heat exchangers. Using three-dimensional numerical simulations, we examined the heat transfer per unit area and the volume of the pressure drop, comparing these findings with a traditional parallel tube heat exchanger. This innovative design strategy involved arranging zigzag-shaped tubes at varying distances, and the thermal transfer and frictional characteristics were tested at different air speeds. This research suggests that the introduction of zigzag heat exchangers, as opposed to traditional fin-and-tube designs, led to a significant improvement in heat transfer. This enhancement is attributed to the swirling flow created around the zigzag tubes, which increased the total heat transfer area. Furthermore, we found that the heat transfer area increased by 14.2%, 32.1%, and 63.9% for tube zigzag angles of 30°, 45°, and 60°, respectively, when compared to a parallel tube heat exchanger. Consequently, the zigzag-shaped tube heat exchanger demonstrated not only superior heat transfer, but also a reduction in frictional pressure loss.

A Prediction Model to Cost-Optimize Clean-Out of Permeable Interlocking Concrete Pavers

Permeable Interlocking Concrete Paver (PICP) systems provide onsite stormwater management by detaining runoff and removing contaminants. However, a major problem with PICPs is the significant maintenance cost associated with their clean-out to restore the original functionality, which discourages landowners and municipalities from adopting the systems. A combination of laboratory experiments and machine-learning techniques are applied to address this challenge. A total of 376 laboratory experiments were conducted to investigate four independent variables (cleaning equipment speed over the pavement, air speed in the cleaning jets, top opening width of the cupule, and filter media gradation) that affect the cleaning of PICPs. The Buckingham Pi-Theorem was used to express the four main input variables in three dimension-less parameters. This current investigation provides a novel understanding of variables affecting the sustainable and economically feasible maintenance of PICPs. A new model is derived to more accurately predict the percentage of mass removal from PICPs during clean-out using a machine-learning technique. The Group Method of Data Handling (GMDH) model exhibits high performance, with a correlation coefficient (R2) of 0.87 for both the training and testing stages. The established simple explicit equation can be applied to optimize the maintenance costs for industrial applications of Regenerative Air Street Sweepers for sustainable and cost-effective PICP maintenance. Pavements with larger surface areas are found to have lower maintenance costs ($/m2/year) compared to the ones with smaller surface areas. This study estimates $0.32/m2/year and $0.50/m2/year to maintain pavements with larger (5000 m2) and smaller (1000 m2) surface areas, respectively.

Research on Control Strategy of Polar Unmanned Vehicle Wind Power Generation System

Due to the abundant scenery resources in Antarctica, for the unmanned vehicle working in the polar region, the scenery power supply system is built on it, and the control strategies for wind power systems is studied. The max power of the system is tracked by the climbing method, and the variable pitch control ensures that the output power of the generator is near the rated power when the air speed exceeds the rated air speed of the wind turbine. The system is modeled using Matlab/Simulink, and the two control methods are simulated. The simulation results of the system as a whole show that the control strategy can ensure the stable and reliable operation of the system under the environmental conditions of extreme cold and strong wind.

Prospects of thermal comfort management process automation

Purpose. Increasing the efficiency of the building's energy system by taking into account the interrelationship of energy sources, thermal protection, indicators of thermal comfort and microclimate parameters of the premises. Taking into account the changes in the requirements of the European Union for indoor temperature and modern economic challenges, the main goal is to develop a system for automatic control of thermal comfort in a given temperature range with minimization of energy costs. Today, there are already many installed heating and cooling air systems. Based on this, the development of a universal device for maintaining thermal comfort in the room is promising. The methods. To conduct an analysis of the developed approaches to increase the efficiency of the energy system of the building in terms of thermal comfort, to determine the features and possibilities of the energy analysis of heat and taking into account the limitations of human thermal comfort. Findings. The proposed structure of the thermal comfort regulator will make it possible to develop a universal regulator that can be used in heating and air cooling systems, or in combined systems. Improving the quality of indoor temperature control can be achieved by directly managing thermal comfort based on the predicted average PMV score and the predicted percentage of dissatisfied PDD. The originality. Typical approaches to managing indoor comfort based on temperature do not take into account radiation, humidity, air speed, clothing and user load, which leads to both the creation of uncomfortable conditions and excessive use of energy resources. For the first time, in accordance with DSTU B EN ISO 7730:2011, the structure of the thermal comfort control system was proposed, its input and output parameters and ways of obtaining non-measurable parameters were defined. The control system based on the predicted average PMV score and the predicted percentage of dissatisfied PDD determines the level of thermal comfort in the room and reduces the number of dissatisfied users. Management based on the predicted average PMV score ensures a reduction in the use of energy resources while maintaining the minimum acceptable thermal comfort indicators. Practical implementation. The resulting structure can be used in the development of new thermal comfort control systems. Taking into account the presence of a large number of already existing heating and air cooling systems, it is proposed to use thermal comfort regulators to improve the quality of their functioning. The proposed approach through the use of the thermal comfort model will make it possible to determine the heating needs under different comfort conditions, reduce the energy consumption of the building without harming human health, and assess the possibility of increasing energy efficiency by changing the comfort conditions, thermal protection parameters and the microclimate of the premises.

Study on Electromagnetic Relationship and Dynamic Characteristics of Superconducting Electrodynamic Maglev Train on Curved Track

This study considers an electrodynamic maglev train of the MLX01 type as the research object. Equivalent circuit models of levitation/guidance were established, and forces in different directions were solved using the energy method A field-circuit-motion coupling numerical model of a single bogie and a ground coil was established. Based on the field-circuit-motion coupling model, the various electromagnetic relationship of maglev train on curved track was analyzed. The law of the electromagnetic spring coefficient and the internal mechanism under different electromagnetic parameters was explored. Considering the coupling characteristics between the electromagnetic forces, the characteristics of the levitation force and guidance force under different standard air gaps were analyzed, and a numerical fitting analysis was performed. On this basis, the laws of levitation force and guidance force with levitation displacement and guidance displacement, as well as the characteristics of drag force with operation speed under different standard air gaps, were studied. Meanwhile, the characteristics of the guidance-drag ratio and levitation-drag ratio were analyzed. A dynamic model with 20 degrees of freedom was established based on the analysis of the geometric model of the maglev train. Taking the track irregularity as the external excitation source of the bogie, the dynamic characteristics of the bogie and vehicle body under different standard air gaps and speeds were analyzed. The effects of different suspension damping and stiffness coefficients on the vibration characteristics of a vehicle body were studied. This provides important theoretical and data support for design and dynamic analysis of superconducting electrodynamic maglev trains.

Hyperspectral Detection of Moisture Content in Rice Straw Nutrient Bowl Trays Based on PSO-SVR

In the process of rice straw nutrient bowl tray drying, real-time detection of changes in moisture content to achieve automatic adjustment of drying factors is one of the important means to ensure its drying quality. At present, the main method for measuring the moisture content of rice straw nutrient bowl trays is the drying and weighing method. This method is not only time consuming, labor intensive, and complex to operate, but also has poor real-time performance, which cannot meet the demand for real-time detection of the moisture content in the production process of rice straw nutrient bowl trays. In this regard, a real-time moisture content detection method for rice straw nutrient bowl trays based on hyperspectral imaging technology was studied. In this study we took the rice straw nutrient bowl tray during the drying process as the research object, adopted a single factor experiment, took microwave power, hot air temperature, and hot air speed as the drying factors, and took the moisture content of the rice straw nutrient bowl tray as the drying index. The rice straw nutrient bowl tray was dried according to the designed drying conditions. When drying, we removed the rice straw nutrient bowl tray every 5 min for weighing and collected hyperspectral image data within the wavelength range of 400~1000 nm until its quality remained unchanged. A total of 204 samples were collected. Using the average spectrum of the region of interest as the sample for effective spectral information, spectral preprocessing was performed using multivariate scattering correction (MSC), standardization normal variables (SNV), and Savitzky–Golay convolution smoothing (SG) methods. Principal component analysis (PCA) and competitive adaptive reweighting (CARS) methods were adopted for the dimensionality reduction of the spectral data. Three prediction models of rice straw nutrient bowl tray moisture content, namely random forest regression (RF), particle swarm optimization support vector regression (PSO-SVR), and XGBoost model were constructed using the reduced dimension spectral data. Finally, the performance of the model was compared using the coefficient of determination (R2) and mean square error (RMSE) as evaluation indicators. The research results indicate that the PCA-PSO-SVR model established based on SG method preprocessing has the best predictive performance, with a training set decision coefficient R2C of 0.984, a training set mean square error RMSE-C of 2.775, a testing set decision coefficient R2P of 0.971, and a testing set mean square error RMSE-P of 3.448. The model therefore has a high accuracy. This study achieved rapid detection of water content in rice straw nutrition trays. This method provides a reliable theoretical basis and technical support for the rapid detection of rice straw nutrient bowl tray moisture content, and is of great significance for improving the quality of rice straw nutrient bowl trays; promoting the popularization and application of raising rice straw nutrient bowl tray seedlings and whole process mechanized planting technology system; improving soil structure; and protecting the ecological environment.

Impacts of usage conditions on performance of ozone removal devices in ventilation systems

Ozone removal devices can be exposed to a wide range of environmental and operating conditions in building ventilation systems, which can affect their ozone removal performance. We evaluated activated carbon and metal oxide filters under varying temperature, relative humidity, ozone concentration, and air speed, as well as after no-ozone periods. Results on new activated carbon filters show that decreasing relative humidity from 50% to 30% decreased single-pass efficiency by 6% relatively at 70 ppb ozone and nearly doubled the degradation rate at 500 ppb ozone; increasing relative humidity to 80% had no effect on efficiency; increasing temperature from 25 to 35 °C increased single-pass efficiency at 70 ppb ozone by 11% relatively and decelerated aging by 22% relatively at 500 ppb ozone. The observed dual effect of water indicates that water can facilitate chemical reactions between ozone and activated carbon, but it can block reactive sites on activated carbon at a high relative humidity. The tested activated carbon and manganese dioxide filters were not sensitive to ozone concentration ranging from 35 to 500 ppb. Activated carbon filters recovered 1%–3% efficiency after 16-h ozone breaks probably due to decomposition of surface oxygen complexes. An air speed increase from 0.6 to 2.7 m/s significantly decreased the single-pass efficiency of all tested devices. A plug flow reactor model proved useful in predicting the impact of air speed on single-pass efficiency as well as the non-linear relationship between single-pass efficiency and time.

Smelling Peppers and Pout Submitted to Convective Drying: Mathematical Modeling, Thermodynamic Properties and Proximal Composition.

Pepper (Capsicum spp.) is among the oldest and most cultivated crops on the planet. Its fruits are widely used as natural condiments in the food industry for their color, flavor, and pungency properties. Peppers have abundant production; on the other hand, their fruits are perishable, deteriorating within a few days after harvesting. Therefore, they need adequate conservation methods to increase their useful life. This study aimed to mathematically model the drying kinetics of smelling peppers (Capsicum chinense) and pout peppers (Capsicum chinense Jacq.) to obtain the thermodynamic properties involved in the process and to determine the influence of drying on the proximal composition of these peppers. Whole peppers, containing the seeds, were dried in an oven with forced air circulation, at temperatures of 50, 60, 70, and 80 °C, with an air speed of 1.0 m/s. Ten models were adjusted to the experimental data, but the Midilli model was the one that provided the best values of coefficient of determination and lowest values of the mean squared deviation and chi-square value in most of the temperatures under study. The effective diffusivities were well represented by an Arrhenius equation, appearing in the order of 10-10 m2·s-1 for both materials under study, since the activation energy of the smelling pepper was 31.01 kJ·mol-1 and was 30.11 kJ·mol-1 in the pout pepper, respectively. Thermodynamic properties in both processes of drying the peppers pointed to a non-spontaneous process, with positive values of enthalpy and Gibbs free energy and negative values of entropy. Regarding the influence of drying on the proximal composition, it was observed that, with the increase in temperature, there was a decrease in the water content and the concentration of macronutrients (lipids, proteins, and carbohydrates), providing an increase in the energy value. The powders obtained in the study were presented as an alternative for the technological and industrial use of peppers, favoring obtaining a new condiment, rich in bioactives, providing the market with a new option of powdered product that can be consumed directly and even adopted by the industry as a raw material in the preparation of mixed seasonings and in the formulation of various food products.

Characteristic and kinetic study of the hot air-drying process of artificial limonite pellets

BackgroundLimonite pellets, primarily composed of Fe2O3·nH2O, are a crucial raw material for modern iron-making techniques. In order to produce high-quality pellets, a pre-drying and roasting process is necessary. This is because wet pellets can absorb heat during the water evaporation process, which can lead to uneven temperature distribution in the blast furnace. MethodsIn this study, we investigated the hot air-drying processes of limonite pellets. Specifically, we examined the impacts of temperature and air speed on pellet quality, weight loss, moisture content, and drying rate to identify optimal drying process parameters for artificial limonite pellets. Additionally, we analyzed the drying kinetics of synthetic limonite pellets using experimental data. Significant FindingsThe results show that the drying rates of the pellets increase with temperature and wind speed and that Correction Page(III) is suitable for the kinetic drying model of synthetic limonite pellets. This research provides important theoretical and practical insights into drying limonite pellets in real-world production processes.

Numerical simulation study on the exhaust gas migration of fuel vehicles under an airflow field in the confined space of an underground coal mine

As the main tool for transporting people and materials in coal mines with inclined shafts, fuel vehicles easily cause exhaust gas accumulation and significant pollution due to the special underground environment. In this paper, the problem of exhaust gas migration under the action of a special airflow field in underground confined space is studied. First, a physical model of exhaust gas migration in the confined space of an underground coal mine is established. By combining numerical simulations with field measurements, the law of exhaust gas migration of fuel vehicles under the action of an airflow field in a confined space is studied. The results show that the migration and diffusion of CO gas in exhaust gas are affected by airflow, and the concentration decreases with an increasing distance. The main irregular pollution area is concentrated within one meter of the space behind the vehicle. The pollution area of more than 24 ppm is approximately 0.124 m2, the pollution length is approximately 0.767 m, and the pollution width and height are 1.16 m and 1.83 m, respectively. In the adjustable range of the research conditions and air speed, the increase in the air speed can accelerate the dilution of CO gas, but it needs to be maintained in a reasonable air speed range. In this paper, a theoretical basis for exploring the migration and distribution of fuel vehicle exhaust pollution in confined spaces is provided.